Description of a New Sound Produced by Nassau Grouper at Spawning Aggregation Sites

AbstractAcoustic telemetry is a widely used technique employed to better understand fish movement patterns across seascapes. Traditionally, surgical acoustic transmitter implantation is conducted at the surface, resulting in a high degree of uncertainty as to the post-release survival of the fish and the validity of the results attained from these experiments. Few studies have conducted In situ tagging, where the capture, tagging, and release are completed entirely at the depth in which the fish occurs naturally. Through the use of closed-circuit rebreather (CCR) technology, this study outlines the first known practical application of the methodology performed at mesophotic depths. In six dives conducted at depths between 40 and 50 m, a total of 10 Nassau grouper were tagged at a spawning aggregation off the west coast of Puerto Rico. The total time (time divers arrived at the trap to time of release) for each procedure was approximately 12 min, after which all fish were released and observed without indication of stress or physiological impairment. Short-term tracking of tagged fish revealed a 100% post-surgery survival rate with maximum detection of 347 days post-surgery. Survival rates of this nature have not been quantified or reported from other tagging studies, allowing the researchers to conclude that this methodology, coupled with the efficiency provided by CCR at these depths, enhanced survivorship and bias for studies utilizing acoustic telemetry.

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Patterns of color phase indicate spawn timing at a Nassau grouper Epinephelus striatus spawning aggregation

Current Zoology ◽

10.1093/czoolo/58.1.73 ◽

2012 ◽

Vol 58 (1) ◽

pp. 73-83 ◽

Cited By ~ 9

Author(s):

Stephanie K Archer ◽

Scott A Heppell ◽

Brice X Semmens ◽

Christy V Pattengill-Semmens ◽

Phillippe G Bush ◽

...

Keyword(s):

Relative Proportion ◽

Video Camera ◽

Marine Conservation ◽

Spawning Aggregation ◽

Cayman Islands ◽

Spawning Aggregations ◽

Nassau Grouper ◽

Epinephelus Striatus ◽

Spawning Periods ◽

White Belly

Abstract Nassau grouper Epinephelus striatus are a large bodied, top level predator that is ecologically important throughout the Caribbean. Although typically solitary, Nassau grouper form large annual spawning aggregations at predictable times in specific locations. In 2003, The Cayman Islands Marine Conservation Board established protection for a newly rediscovered Nassau grouper spawning aggregation on Little Cayman, British West Indies. The large size of this aggregation provides a unique opportunity to study the behavior of Nassau grouper on a relatively intact spawning aggregation. During non-spawning periods Nassau grouper display a reddish-brown-and-white barred coloration. However, while aggregating they exhibit three additional color phases: “bicolor”, “dark”, and “white belly”. We video sampled the population on multiple days leading up to spawning across five spawning years. Divers focused a laser caliper equipped video camera on individual fish at the aggregation. We later analyzed the video to determine the length of the fish and record the color phase. Our observations show that the relative proportion of fish in the bicolor color phase increases significantly on the day leading up to the primary night of spawning. The increase in the proportion of the bicolor color phase from 0.05 early in the aggregation to 0.40 on the day of spawning suggests that this color phase conveys that a fish is behaviorally and physiologically prepared to spawn. Additionally, 82.7% of fish exhibiting dark or white belly coloration early in the aggregation period suggests that these color phases are not only shown by female fish as was previously posited.

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